Chemotherapy is usually ineffective for lung cancer due to chemoresistance. The anticancer activity of chemotherapeutics is mainly through the killing of cancer cells. Tremendous efforts on apoptosis resistance-related mechanisms have moderately improved lung cancer chemotherapy, suggesting other mechanisms are critical in chemoresistance. Recent studies suggest that therapeutics can induce RIP3- mediated necroptosis to kill tumor cells that are resistant to apoptosis. However, cancer cells may develop necroptosis-evading capacities. Our preliminary studies found: (1) RIP3 expression is suppressed in 22% of human lung cancer tissues; (2) RIP3 promoter hypermethylation is associated with RIP3 suppression; (3) restoring RIP3 expression significantly increased sensitivity of lung cancer cells to cisplatin; (4) forced RIP3 expression enhanced cisplatin-induced necroptosis; and (5) sensitizing necroptosis increased chemosensitivity. Thus, we hypothesize that the necroptosis pathway is impaired in some human lung cancers and sensitizing necroptosis will improve chemotherapy efficacy and overcome chemoresistance in these lung cancers. The hypothesis will be tested in three specific aims: (1) To determine if sensitizing necroptosis overcomes chemoresistance in lung cancer cells; (2) To determine if epigenetic and post- transcriptional regulation of RIP3 underlies the mechanisms of necroptosis suppression-associated chemoresistance in human lung cancer; and (3) To determine if RIP3 re-expression sensitizes necroptosis and overcomes chemoresistance in human NSCLC xenografts in nude mice. The goal of this application is to obtain more supportive evidence validating the role of necroptosis in lung cancer's clinical response to first-line chemotherapy and chemoresistance. Positive results from this project will be a solid foundation for an R01 application with comprehensive mechanistic and translational studies for improving the efficacy of chemotherapy against lung cancer.